Carbon dioxide is a chemical compound made of carbon and oxygen. Carbon dioxide is a colorless and odorless gas. At low concentration, it is a natural component of air and arises in living organisms during cell respiration, but also during the combustion of carbonaceous substances with sufficient oxygen. Since the beginning of industrialization, the CO2 component in the atmosphere has significantly increased. The main reasons for this are the CO2 emissions caused by humans—known as anthropogenic CO2 emissions.
The carbon dioxide in the atmosphere absorbs a part of the thermal radiation. This property makes carbon dioxide into a greenhouse gas and is one of the causes of the greenhouse effect.
For these and also other reasons, research and development is currently being performed in greatly varying directions to find a way of reducing the anthropogenic CO2 emissions. There is a great need for CO2 reduction in particular in connection with energy production, which is frequently performed by the combustion of fossil energy carriers, such as coal or gas, but also in other combustion processes, for example, during garbage combustion. Hundreds of millions of tons of CO2 are released into the atmosphere every year by such processes.
The fuels required for producing heat generate CO2, as explained at the beginning. Up to this point, no one has arrived at the idea of using the sand provided in oil-bearing sands (SiO2), oil-bearing shale (SiO2+[CO3]2), in bauxite, or tar-bearing sands or shales, and other mixtures to reduce the CO2 discharge and, in addition, obtain new raw materials and above all energy from the products of such a novel method.
Instead of using naturally occurring mixtures of sand and oil in this novel method, industrial or natural wastes containing hydrocarbons, possibly after admixing with sand, may also be used. Using natural asphalt (also referred to as mineral pitch) instead of the oil component is also conceivable. A mixture made of asphalt with pure sand or with construction rubble which contains a sand component is especially preferable.
However, water glass, a mixture of sand with acid or base, may also be used, the water glass being admixed with mineral oils in order to provide the hydrocarbon component necessary for the present invention (microemulsion method).
The present invention may also be used particularly advantageously for cleaning beaches and sand banks contaminated after a tanker accident, for example. A vehicle is best suitable for this purpose, preferably a ship which is equipped with one or more reaction areas according to the present invention. Therefore, the contaminated sand, including heavy oil, may thus be processed on location and converted into valuable products without stressing the environment. Energy is obtained at the same time.
The reserves of oil-bearing sands (SiO2) and shales (SiO2+[CO3]2) are known to exceed the world oil reserves multiple times over. The technical methods applied for separating oil and minerals are currently ineffective and too costly. Natural asphalt occurs at multiple locations of the earth, but is currently mined at commercial scale primarily in Trinidad.
Sand occurs in greater or lesser concentrations everywhere on the surface of the earth. A majority of the sand occurring comprises quartz (silicon dioxide; SiO2).
However, silicon components are also present in gneiss, mica, granite, slate, and bauxite. Therefore, these rocks may also be used.
The object of the present invention is to provide such possible raw materials and describe their technical production. The chemical findings used in the method are characterized in that the silicon present in the sands and shales and other mixtures participate in a reaction, and a reversible hydrogen carrier is provided.
The cascaded sequence of individual reactions (also referred to here as energy-material cascade coupling or EMC2) is characteristic for the present invention. These individual reactions are coupled to one another in such a way that either the amount of energy released increases with each reaction step, or other (preferably higher-value or higher-energy) reaction products are provided with each reaction step. For this purpose, the individual reaction areas/zones in which partial reactions run are connected to one another thermally and/or for the transfer of reactants.
In addition, it is an object to provide alternative possible approaches for generating and providing energy in the form of reversible hydrogen carriers, which are transportable harmlessly, and providing the hydrogen at the consumer.
According to the present invention, in a first partial reaction in a power plant process, silicon is obtained from one or more of the following starting materials: oil sand, oil shale, bauxite, gneiss, mica, granite, or slate. The use of the number “1” is not to indicate that this partial reaction is executed first. A blend of one or more of the cited starting materials is possibly used in the scope of this first partial reaction, which is liquefied by adding an acid or base, to improve the transportability through pipes, for example. In this case, the acid or base may be reclaimed again by the heating using the primary energy providers.
A preferred embodiment of the present invention exploits, inter alia, the fact that silicon (e.g., as a powder at suitable temperature) may be reacted directly after ignition with pure (cold) nitrogen (e.g., nitrogen from the ambient air) to form silicon nitride, because the reaction is strongly exothermic. The heat arising may be used in reactors, for example, in power plant processes. This reaction of silicon to form silicon nitride is referred to here as the second partial reaction.
The silicon arising in the first partial reaction according to the present invention in power plant processes from oil sand, oil shale, bauxite, gneiss, mica, granite, and/or slate is surface-active and may be treated catalytically (e.g., using magnesium and/or aluminum as a catalyst) with hydrogen, so that monosilane results. This reaction of silicon to form monosilane is referred to here as the third partial reaction. This monosilane may be removed from the reaction chamber and subjected a further time to a catalytic pressure reaction in another location (fourth partial reaction). According to the equation
Si+SiH4→(Using catalysts such as Pt, etc.)→Si(SiH4)+SiHn(SiH4)m+SinHm long-chain silanes may be prepared, which may be used both in the technology of fuel cells and in engines. The silanes are a possible form of a reversible hydrogen carrier.
However, silicon (such as silicon powder) may also be nitrated in the process according to the present invention in nitrogen (N2) atmosphere at temperatures of approximately 1400° C. to form silicon nitride Si3N4. This type of reaction is a variation of the second partial reaction.
The silicon nitride may then be converted into NH3, for example, using hydrolysis. An example of the reaction running in such a hydrolysis is provided in the following equation:Si3N4+6 H2O→3 SiO2+4 NH3 
Thus, NH3 and silicon dioxide arise in this reaction. NH3 is an outstanding hydrogen carrier. Because the hydrolysis of silicon nitride runs relatively slowly, the silicon nitride is used according to the present invention either as flakes, as a powder, or in porous form. A significantly larger surface thus results, which makes the hydrolysis of the silicon nitride much more efficient and rapid. This approach is based on the finding that in the hydrolysis of silicon nitride, surface hydrolysis plays an essential role. The hydrolysis thus becomes more efficient due to the intentional enlargement of the surface of the silicon nitride. The reaction of silicon nitride to form NH3 using hydrolysis is referred to here as the fifth partial reaction. The use of Si3N4 nanostructures or nanocrystals is especially effective here, which may be obtained from a sol-gel process, for example. The energy for the sol-gel process may in turn be taken from one of the partial reactions according to the present invention.
The silicon, the NH3, but also the silanes are outstanding energy providers, which may be conveyed to a consumer without problems, in order to cleave off hydrogen there. However, hydrogen peroxide is better suitable as an energy provider. The hydrogen peroxide may be generated in a further partial reaction according to the present invention, which is coupled to a power plant process or integrated in such a process. This is also true for the production of silicon, NH3, or silanes, which may also be integrated in such a power plant process or coupled to such a process.
Further details and advantages of the present invention are described in the following on the basis of exemplary embodiments.
Various aspects of the present invention are schematically illustrated in the figures of the drawing: